There are many situations in which it is necessary to monitor the turbidity of a body of fluid. Turbidity is the cloudiness or haziness of a fluid caused by large numbers of individual particles. This invention relates to the measurement of turbidity, or cloudiness, in liquids held in a receptacle, such as a bottle. One common use of a measurement of turbidity is in monitoring cell cultures in microbiology laboratories. The higher the turbidity, the higher the cell number density in the cell culture. The description of the invention will be in the context of cell culture; however, this patent application is intended to cover many other uses where turbidity needs to be measured, in laboratory and field work, in medicine, in various industries such as pharmaceutical, food, beverage etc., as well as hydrology, in general, and drinking water quality control in particular.
The prevalent method of monitoring a cell culture, for instance, of Escherichia Coli bacteria, in order to detect the right time for an intervention, is to take out a sample using a pipette, and to insert the sample in a cuvette that is then inserted in a spectrophotometer for turbidity measurement. There are drawbacks to this method. First of all, it exposes the cell culture to the risk of contamination. Secondly, it takes time. Minor nuisances of the conventional method include the partial loss of culture due to sampling, the expense of a pipette tip, and the need to wash the cuvette.